Table 1.
Open source and commercial sensor and data logger configurations and 2–pt calibration standards.
Fig 1.
Block diagram of sensor configurations evaluated for this study.
A) Open source (OS) Atlas Electrical Conductivity (EC) sensor configuration includes an Atlas EC probe connected to an Atlas Conductivity Circuit EZO and circuit carrier board using either a 7.5–m or 30–m extension cable and then connected to an OS Arduino Mega 2560 Rev3 data logger using jumper cables. B) OS/commercial (OS/C) hybrid Decagon EC sensor configuration includes a Decagon CTD–10 conductivity, temperature, and depth sensor and 10–m cable with a 3–wire pigtail connector connected to an OS Arduino Mega 2560 Rev3 data logger. C) Commercial YSI Instruments EC300A handheld meter and EC probe with a 1–m cable. Commercial Decagon EC sensor configuration includes a Decagon CTD–10 sensor with a 10–m cable with a stereo plug connected to a Decagon RM50 data logger. The OS Atlas and OS/C Decagon EC sensor configurations are powered directly by the Arduino, which is powered by an external 12 V power supply and a 5 V step–down voltage regulator connected to a breadboard using jumper cables.
Fig 2.
Flowchart for evaluating electrical conductivity sensor accuracy and precision.
Fig 3.
The effect of sensor cable length and sensor calibration on electrical conductivity sensor accuracy.
OS, open source; C, commercial; OS/C, open source/commercial hybrid; m, meters; NA, not applicable (i.e., not measured). OS electrical conductivity (EC) sensor configurations include 1) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 2) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 3) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm); and 4) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm). EC measurements were temperature corrected to 25° C and recorded as specific conductance (SC, units in μS/cm).
Fig 4.
The effect of sensor cable length and sensor calibration on electrical conductivity sensor precision when measuring the 84 μS/cm reference standard.
OS, open source; C, commercial; OS/C, open source/commercial hybrid; m, meters. OS electrical conductivity (EC) sensor configurations include 1) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 2) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 3) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm); and 4) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm). EC measurements were temperature corrected to 25° C and recorded as specific conductance (SC, units in μS/cm).
Fig 5.
The effect of sensor cable length and sensor calibration on electrical conductivity sensor precision when measuring the 1413 μS/cm reference standard.
OS, open source; C, commercial; OS/C, open source/commercial hybrid; m, meters. OS electrical conductivity (EC) sensor configurations include 1) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 2) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 3) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm); and 4) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm). EC measurements were temperature corrected to 25° C and recorded as specific conductance (SC, units in μS/cm).
Fig 6.
The effect of sensor cable length and sensor calibration on electrical conductivity sensor precision when measuring the 2060 μS/cm reference standard.
OS, open source; C, commercial; OS/C, open source/commercial hybrid; m, meters. OS electrical conductivity (EC) sensor configurations include 1) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 2) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “narrow” 2–point calibration (i.e., 84 and 1413 μS/cm); 3) Arduino data logger connected to an Atlas EC sensor with a 7.5–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm); and 4) Arduino data logger connected to an Atlas EC sensor with a 30–m cable and calibrated with a “wide” 2–point calibration (i.e., 84 and 2060 μS/cm). EC measurements were temperature corrected to 25° C and recorded as specific conductance (SC, units in μS/cm).
Table 2.
Open source and commercial electrical conductivity sensor precision.